Re: [Qemu-devel] [RFC PATCH] powerpc: add PVR mask support

[Anthony Liguori <anthony@codemonkey.ws>]

Andreas Färber <afaerber@suse.de> writes:

> Am 15.08.2013 15:12, schrieb Anthony Liguori:
>> Everyone is talking past each other and no one is addressing the real
>> problem.  There are two distinct issues here:
>> 
>> 1) We have two ABIs that cannot be changed unless there's a very good
>>    reason to.  Alexey's original patch breaks both.  The guest ABI
>>    cannot change given a fixed command line.
>> 
>>    IOW, the exposed PVR value for -cpu POWER7 cannot change across
>>    versions of QEMU or when running on different hardware.  This breaks
>>    live migration and save/resume.
>> 
>>    We also cannot break the command line interface.  If the last version
>>    of QEMU supported -cpu POWER7_v2.1, then we must continue to support
>>    that.
>
> 1a) How should -cpu 0xDEADBEEF or -cpu DEADBEEF behave.
>
>     I expect it to error out as before

Correct although that can't be guaranteed.  Maybe there is a 'DEADBEEF'
cpu model in the future.  This is the architecture of the ripvanwinkle
and eieio instructions after all :-)

>     rather than applying the same fuzz/mask that -cpu host might.

Fuzzing CPU models sounds like an awful idea to me.

Regards,

Anthony Liguori

>     That would let us implement our own fuzz logic in kvm.c,
>     operating on a GSList of ObjectClasses to handle multiple matches.
>
> Regards,
> Andreas